Okay, I experimented with the game and got to a final conclusion:
The “ending” you get at the end of the demo is based on how much CLEAR TIME (from start to finish; if you die, the time after your last save is erased and only the time before your last save is kept in mind) it takes you to complete the game, so no collectables, no unlockables (so far in the demo, you can only miss 'AGENTS' scenes), no secrets, no items, etc. impacts your “ending.”
I managed to get 2 other ranks, a PRIVATE and a TRAINEE. I might have missed a rank between those two, I kept the game running for quite long without supervision (an hour and a half probably, I gave up counting it at that point xF). Then again, what other clothing than underwear and overalls can a cosmobreeder have under his/her spacesuit, when he'll strip them off anyway to research? You tell me!
And... I spent too much time wrting this, so I am going to just... stop writing more nonsense and go on with my life. Here are the screens of the other two “endings” for reference and I'm out of this essay heck:
